perfmonctl(2) Linux Man Page

Name

perfmonctl - interface to IA-64 performance monitoring unit

Synopsis

#include <syscall.h> 
#include <perfmon.h> 
long perfmonctl(int " fd ", int " cmd ", void " arg [. narg "], int " narg ");

Note : There is no glibc wrapper for this system call; see HISTORY.

Description

The IA-64-specific perfmonctl() system call provides an interface to the PMU (performance monitoring unit). The PMU consists of PMD (performance monitoring data) registers and PMC (performance monitoring control) registers, which gather hardware statistics.

perfmonctl() applies the operation cmd to the input arguments specified by arg. The number of arguments is defined by narg. The fd argument specifies the perfmon context to operate on.

Supported values for cmd are:

PFM_CREATE_CONTEXT

Set up a context.

The fd parameter is ignored. A new perfmon context is created as specified in ctxt and its file descriptor is returned in ctxt->ctx_fd.

The file descriptor can be used in subsequent calls to perfmonctl() and can be used to read event notifications (type pfm_msg_t ) using read(2). The file descriptor is pollable using select(2), poll(2), and epoll(7).

The context can be destroyed by calling close(2) on the file descriptor.

PFM_WRITE_PMCS

Set PMC registers.

PFM_WRITE_PMDS

Set PMD registers.

PFM_READ_PMDS

Read PMD registers.

PFM_START

Start monitoring.

PFM_STOP

Stop monitoring.

PFM_LOAD_CONTEXT

Attach the context to a thread.

PFM_UNLOAD_CONTEXT

Detach the context from a thread.

PFM_RESTART

Restart monitoring after receiving an overflow notification.

PFM_GET_FEATURES

PFM_DEBUG

If val is nonzero, enable debugging mode, otherwise disable.

PFM_GET_PMC_RESET_VAL

Reset PMC registers to default values.

Return Value

perfmonctl() returns zero when the operation is successful. On error, -1 is returned and errno is set to indicate the error.

Standards

Linux on IA-64.

History

Added in Linux 2.4; removed in Linux 5.10.

This system call was broken for many years, and ultimately removed in Linux 5.10.

glibc does not provide a wrapper for this system call; on kernels where it exists, call it using syscall(2).